Various circuits for demodulating radio data signals that process analog signals are already known.
Some transmitters radiate a radio data signal (RDS) and traffic announcement signals, known as ARI signals. Other transmitters may radiate only radio data signals (RDS), while still others may only radiate ARI signals. Both the RDS and the ARI signals are radiated with a carrier signal of 57 kHz. For RDS signals, the carrier is suppressed. A receiver, thus, may receive a multiplex signal from one transmitter or, depending on its physical location, a mix of RDS and ARI signals, or only RDS, or only ARI signals. The receiver, thus, must be capable of recognizing the three possibilities, and distinguishing between the three signals, whether they occur separately or simultaneously.